May 14 (Bloomberg) -- Prime Minister Shinzo Abe said today
the entry by a submarine from an unidentified country into
waters near Japan was a serious matter that must not be allowed
to happen again.

Japan’s Defense Ministry yesterday said it had detected a
submarine traveling under water within its “contiguous zone,”
adjacent to its territorial waters, in Okinawa prefecture on May
12. An unidentified submarine also sailed while submerged into
the contiguous zone on May 2, the ministry said in a statement
posted on its website.

Japan and China are locked in a territorial dispute over
East China Sea islands and their ships and planes have been
tailing one another through adjacent seas for months. Japan said
that a Chinese ship had locked weapons-control radar onto one of
its helicopters in January.

“Coming so close to territorial waters is a serious
action,” Abe told a parliamentary committee in Tokyo. “I am
not going to mention the nationality of the submarine, but we
have already carried out the necessary analysis, including about
its nationality. We want the relevant country to be aware that
this must never happen again.”

Abe said he had decided to make the incidents public
because they occurred close together, giving the impression that
they were intentional. Submarines are required to surface before
entering other countries’ territorial waters in order to prevent
any stealth attack on ships, he told the committee.

The submarine was detected by a P-3C surveillance aircraft
close to the island of Kumejima on May 12, the ministry said. In
the earlier incident, a submarine was spotted close to Amami
Oshima, an island roughly half way between Okinawa and the
southernmost main island of Kyushu, it said.